Crop Research Institute, Hunan Academy of Agricultural Sciences, Changsha 410125, China.
Beijing Key Laboratory of Maize DNA Fingerprinting and Molecular Breeding, Maize Research Center, Beijing Academy of Agriculture and Forestry Sciences, Beijing 100097, China.
J Exp Bot. 2021 Sep 30;72(18):6230-6246. doi: 10.1093/jxb/erab254.
Cadmium (Cd) accumulation in maize grains is detrimental to human health. Developing maize varieties with low Cd content is important for safe consumption of maize grains. However, the key genes controlling maize grain Cd accumulation have not been cloned. Here, we identified one major locus for maize grain Cd accumulation (qCd1) using a genome-wide association study (GWAS) and bulked segregant RNA-seq analysis with a biparental segregating population of Jing724 (low-Cd line) and Mo17 (high-Cd line). The candidate gene ZmHMA3 was identified by fine mapping and encodes a tonoplast-localized heavy metal P-type ATPase transporter. An ethyl methane sulfonate mutant analysis and an allelism test confirmed that ZmHMA3 influences maize grain Cd accumulation. A transposon in intron 1 of ZmHMA3 is responsible for the abnormal amino acid sequence in Mo17. Based on the natural sequence variations in the ZmHMA3 gene of diverse maize lines, four PCR-based molecular markers were developed, and these were successfully used to distinguish five haplotypes with different grain Cd contents in the GWAS panel and to predict grain Cd contents of widely used maize inbred lines and hybrids. These molecular markers can be used to breed elite maize varieties with low grain Cd contents.
镉（Cd）在玉米籽粒中的积累对人类健康有害。培育低镉含量的玉米品种对于安全食用玉米籽粒非常重要。然而，控制玉米籽粒镉积累的关键基因尚未被克隆。在这里，我们使用全基因组关联研究（GWAS）和两亲本分离群体的混池 RNA-seq 分析，鉴定了一个控制玉米籽粒镉积累的主要位点（qCd1），该群体由 Jing724（低镉品系）和 Mo17（高镉品系）组成。通过精细定位和候选基因鉴定，确定了一个编码液泡膜定位重金属 P 型 ATP 转运蛋白的基因 ZmHMA3。乙磺酸乙酯突变分析和等位基因测试证实 ZmHMA3 影响玉米籽粒镉积累。ZmHMA3 内含子 1 中的转座子导致 Mo17 中异常的氨基酸序列。基于不同玉米品系 ZmHMA3 基因的自然序列变异，开发了四个基于 PCR 的分子标记，并成功用于区分 GWAS 面板中不同镉含量的五个单倍型，以及预测广泛使用的玉米自交系和杂交种的籽粒镉含量。这些分子标记可用于培育低镉含量的玉米优良品种。
